The present invention relates to a breaker core for use in a casting process, whereby the disk-shaped breaker core, which is provided with a through-opening for the liquid metal and has a netlike webbing spanning its through-opening, is fixable to the underside of a feeder body to be placed on the casting model and that faces the casting model.
In casting technology, it often is necessary to arrange an additional feeder in the casting mold, whose feeder body is filled with the liquid metal during casting of the casing piece and upon hardening of the casting piece, the feeder body compensate volume deficits that occur, in order to prevent the formation of cavitation shrink holes in the casting piece. In this connection, the feeder must be produced, such that the liquid metal that is fed into it hardens later than the casting piece, so that during the hardening process, a material transport to the casting piece can occur, which sealingly feeds the casting piece. In this regard, the feeders comprise an exothermic and/or insulating material or are formed as so-called natural feeders in the mold sand surrounding the casting model. In the frame of known methods for manufacturing casting molds that are provided with feeders, the feeders are arranged with any desired geometric form on the position to be supplied of the later casting piece on the casting model and with the formation of the casting mold by dealing of the mold sand that is applied, are solidly cast or molded. With another method, during casting of the casting model hollow spaces are produced by means of the mold sand, in which individual feeders made of an exothermic and/or insulating material are subsequently inserted and in this manner, are connected to the mold cavity produced by the demolding of the casting model in the casting mold. Thus, the feeders are arranged as so-called head feeders uniformly on the surface of the casting model or on the later=produced casting piece. A feeder with the above-noted characteristic features is described, for example, in DE 20 2013 104 863 U1.
A problem generally exists when using feeders. Specifically, after casting, hardened casting material in the form of so-called feeder residue remains in the feeder body, which must be removed after removing the casting piece from the feeder body. In order to facilitate this separation, the use of so-called breaker cores is common, which are defined on the feeder body on the underside of the feeder body facing toward the mold cavity of the casting mold. The breaker cores are made of a fire-resistant material and have a through-opening, via which the increasingly hot metal can flow out of the mold cavity of the casting mold into the inner cavity of the feeder body or from there flow further back into the mold cavity. The breaker cores, which are generally manufactured by shooting in a core shooting machine, are disk-shaped, whereby the through-opening is formed by a constriction formed in the disc-shaped breaker core body, in order to produce a predetermined breaking point for breaking off feeder residue from the surface of the casting piece. Such an arrangement of the feeder with a breaker core is described, for example, in WO 2009/103539A1.
Breaker cores now have a netlike webbing which is anchored on the breaker core and which spans the through opening formed by the constriction. These netlike webbings permit the entry of the liquid metal in the cavity of the feeder body or from it back into the mold cavity, but also form a metal layer that is penetrated by the webbing, based on the bathing of the net structure by the hot metal after hardening of the casting piece, and thereby creates a defined material weakness, whereby the existing feeder residue can be knocked off in the course of the webbing layer. Thus, the netlike webbing, with the manufacture of the breaker core, is positioned in the plane of the constriction in the shooting mold and shot with the fire resistance molding material mixture that is used to make the breaker core.
With the arrangement of the netlike webbing in the interior of the breaker core, a spacing of the webbing from the surface of the casting piece is required, so that after breaking off of the feeder residue in the predetermined breaking points formed by the netlike webbing, a part of the feeder residue still remains on the casting part, which in turn, must be still be removed by expensive cleaning processes. Thus, the breaker core represents an additional and in particular, if including a netlike webbing, an expensive component that must be made.